1. Field of the Invention
The present invention is concerned with an interference detection circuit comprising:
gate means having a gate control for preventing interference in an inputted signal from being outputted, and PA1 control means coupled to the gate control for generating a gate control signal. PA1 means for defining a discrimination curve in terms of magnitude and frequency, and PA1 means for detecting whether the combination of the instantaneous magnitude and the instantaneous frequency in the inputted signal exceeds the discrimination curve, in which case, the control means generates the gate control signal.
The present invention is also concerned with a method for detecting interference, wherein an input signal whereon interference is superimposed is prevented from being outputted by gating said input signal by means of a gate control signal.
Furthermore the present invention is concerned with a receiver, comprising a tuner means, a demodulator means having an input coupled with the tuner means and an audio output.
2. Description of the Related Art
Such an interference detection circuit and method are commonly used in the video, or audio field, such as in receivers, car radios, etc., but are also used in measuring equipment and radar appliances.
The generally known interference circuit uses the gate means to leave out that part of the inputted signals on which interference is superimposed. That part is then replaced by a part not polluted with interference.
The known interference circuits suffer from the drawback that the amplitude of detected interferences have to exceed a fixed threshold in order to activate these circuits to generate the gate control signal. Some types of interferences have a small amplitude but can be very disturbing for a relatively weak signal emanating from for example a far away transmitter. Such interferences are poorly detected by the known interference circuits.
Another problem in the prior art circuits is related to the fixing of the threshold. On the one hand this threshold has to be large enough to avoid false interference detection, whereas, on the other hand, this threshold should be low enough to detect annoying interferences.